#
Capacitor Questions

** Q5.**

(a) Define the capacitance of a capacitor.

**(2 marks) **

(b) The circuit shown below contains a battery, a resistor, a capacitor and a switch.

The switch in the circuit is closed at time t = 0. The graph shows how the charge Q

stored by the capacitor varies with t.

**(b) **

(i) When the capacitor is fully charged, the charge stored is 13.2μC. The electromotive force (emf) of the battery is 6.0V. Determine the capacitance of the capacitor.

**(3 marks)**

(ii) The time constant for this circuit is the time taken for the charge stored to increase from 0 to 63% of its final value. Use the graph to find the time constant in milliseconds.

**(2 marks)**

(iii) Hence calculate the resistance of the resistor.

**(1 mark)**

(iv) What physical quantity is represented by the gradient of the graph?

**(1 mark)**

**(c) **

(i) Calculate the maximum value of the current, in mA, in this circuit during the charging process.

**(1 mark)**

(ii) Sketch a graph on the outline axes below to show how the current varies with time as the capacitor is charged. Mark the maximum value of the current on your graph.

**(2 marks)**

**(Total 12 marks)**